The results of precise measurements of the energies of the 2p3/2~1s», and 2p", ls, "muonic x-ray transitions of "Fe, ' Fe, "Fe, "Fe, "Co "Ni, Ni, 'Ni 'Ni, "Ni 'Cu, 'Cu, "Zn ' Zn "Zn, and ' Zn are reported. Using a highly linear digitally stabilized Ge(Li) spectrometer system, the absolute energies and energy shifts between nuclei were measured with total errors of approximately 40 -60 eV (110 eV for ' Zn).The data were analyzed in terms of the Barrett moments ( r"e ")of the nuclear charge distributions from which the equivalent nuclear radii R"and the isotopic and isotonic differences 5R"were computed. Particular attention was given to higher-order corrections of the energies of the muonic states. Appropriate quantumelectrodynamical corrections were calculated to all significant orders. Nuclear polarization corrections for multipole interactions up to and including L = 4 were computed for each isotope. The b, A = 2 isotone shifts SR"for even A isotopes show a strong shell closure effect at Z = 28, which is quite independent of the neutron number. The hX = 2 isotope shifts between even nuclei decrease smoothly and uniformly with increasing N from X = 28 to N = 40 and are essentially independent of Z. This unexpected behavior suggests that the added neutrons interact with the entire proton core rather than with the valence protons. The hN = 1 isotope shift results show a pronounced odd-even staggering effect, which, however, is somewhat smaller than theoretical predictions. The isotone series "Fe-' Co-Ni, which is just below the Z = 28 shell closure, shows strong odd-even staggering, whereas the series»-'Cu-"Zn and 'Ni-'Cu-'Zn just above Z = 28 exhibit only a very small staggering effect, A comparison of the experimental data of the rms radii ( r')'" with the results of spherically constrained Hartree-Fock calculations shows good agreement for all four Zn isotopes and the heavier Ni isotopes ( Ni, Ni, 'Ni), but poor agreement for the Fe isotopes and "Ni. NUCLEAR STRUCTURE, MOMENTS ' 6' '58Fe, 5~Co, 58'6 '6'62'64¹i @'6 Cu, ' Zn; measured muonic x-ray spectra; deduced nuclear charge parameters, isotope and isotone shifts, Calculated quantum-electrodynamic and nuclear-polarization corrections. Compared charge parameters with Hartree-.Fock cal.culations.
We give an overview about latest developments and measurements with the Dresden electron beam ion source family as compact and economically working table-top sources of highly charged ions. The ion sources are potential tools for various applications such as for use in combination with accelerators in medical particle therapy, as charge breeder or ion trap injector, as ion sources for a new generation of focused ion beam devices and for applications together with time-of-flight secondary mass spectrometers.
We have observed a large Mossbauer effect in Fe 57 following Coulomb excitation. Our results indicate that despite the large recoil energy of the nucleus following the Coulomb excitation, the MSssbauer fraction is essentially undiminished.Recently, the presence of recoilless emission of y rays from nuclei which have been excited by processes which impart large recoil energies to the excited nuclei has been reported by others. 1 " 4 The observation of a large MOssbauer effect in Fe 57 is significant for the investigation of these phenomena.Coulomb excitation was produced by a 1.5-/iA beam of 3-MeV alpha particles from the Johns Hopkins University Van de Graaff accelerator. The target and absorber were 1.9 mg/ cm 2 of 91% enriched Fe 57 . The target was thermally coupled to an aluminum backing which was cooled by contact with an alcohol-dry-ice mixture.The recoilless emission of the 14.4-keV level was observed following Coulomb excitation of the 137-keV level. The 14.4-keV y ray was detected in coincidence with the preceding 122-keV y ray (Fig» 1) 0 This was necessary due to the large Mossbauer fraction which allowed self-absorption in the target making it difficult to observe directly the 14.4-keV line in the presence of x rays and bremsstrahlung background.The detectors were thin Nal(Tl) crystals. The coincidence circuit had a resolving time of 0.5 /isec. The coincidence technique reduced the total background to less than 8 %. The rate of 137-keV level excitation to be expected was calculated according to Alder et al. 5 and was in agreement with the rate of 122-keV y rays observed. On the basis of the 122-keV y-ray counting rate, one can estimate the number of 14.4-keV y rays which should be detected in the absence of nuclear resonant self-absorption. However, the observed coincidence count-ing rate of 3 counts per second was several times less than that expected from this calculation. The existence of self-absorption in the target suggests that perhaps a correction should be made to the E2 nuclear matrix element for the 14.4-keV transition as reported by Thomas and Grace. 6 The width and depth of the absorption dips indicate that the difference in hyperfine splitting between source and absorber is less than 10%. Additional spectra including all the hyperfine lines will be taken to obtain a more accurate determination of the hyperfine splitting of the Coulomb-excited nucleus.The central absorption dip, uncorrected for background, is 17% of the nonresonant transmission (Fig. 2). Because of the very thick target and uncertainties due to vibrations, it is difficult to obtain a value for/, the Mossbauer fraction for the source. Comparison of the Coulomb-excitation results with those ob-5/2" TV 137 kev 3/2" 1/2" >l 100 ns 14.4 kev 57 Fe FIG. 1. Energy-level diagram indicating Coulomb excitation of the 137-keV level. The 14.4-keV y rays were detected in coincidence with the preceding 122-keV y rays. 957
Isotope shifts of the 2p~* Is muonic transition energies in 54 » 56 » 58 Fe have been measured. The results indicate that the charge radii of these isotopes vary approximately as Whereas spherical Hartree-Fock calculations can account for less than one third of the observed isotope shifts, deformed Hartree-Fock results reproduce two thirds of the observed shifts. It is suggested that the remaining discrepancy is primarily due to neglected neutron-proton residual interactions.Since studies of the rearrangement of the nuclear charge distribution in response to the addition of neutrons throughout a series of isotopes provide a stringent test of one's understanding of nuclear structure, we have undertaken a systematic investigation of muonic-atom x rays of separated isotopes in the Ni region. This region is being studied extensively with electron scattering at the University of Mainz, but there has been no thorough muonic investigation of these nuclei. We report here our measurements of the shifts in the 2£ 3/2^l s 1/2 and 2p 1/2 -~ ls 1/2 transition energies for the isotopes 54 » 56 » 58 Fe, along with the results of various Hartree-Fock (HF) calculations of the charge densities of these isotopes. The present results are especially interesting in that they suggest the importance of neglected degrees of freedom in current HF theory. Results on other nuclei in this region will be published separately, along with a full description of our experimental arrangement.The measurements were performed at the Clinton P. Anderson Meson Physics Facility muon channel 1 using isotopically separated Fe 2 O s targets. Data were obtained using a coaxial Ge(Li) detector (full width at half-maximum 1. 8 keV at 1. 3 MeV) in combination with a conventional muon telescope and tar get-identification scintillator arrangement to identify x rays from the three simultaneously measured Fe isotopes. X-ray data from each target were stored separately using an on-line computer. A highly stable, computercontrolled pulser was used for gain stabilization during the runs. Calibration of the Ge(Li) spectrometer was derived from a 60 Co spectrum, which was accumulated during the data run at a rate proportional to the instantaneous intensity of the muon beam. The effect of gain shifts arising from the pulsed (6% duty cycle) nature of the muon beam were thus minimized.The centroids of the 2p-ls lines were determined by least-squares fitting the data with a Gaussian line shape. The fitting procedure took into account the known isotopic impurities of the targets. The probable effect of a reasonable variation in the impurity ratios on the final quoted energies was estimated from a series of fits to the data. The contribution of this uncertainty, less than 8 eV in all cases, is included in the quoted errors. Possible geometrical effects of relative 535
We have characterized ion beams extracted from the Dresden EBIS-A, a compact room-temperature electron beam ion source (EBIS) with a permanent magnet system for electron beam compression, using a pepper-pot emittance meter. The EBIS-A is the precursor to the Dresden EBIS-SC in which the permanent magnets have been replaced by superconducting solenoids for the use of the source in high-ion-current applications such as heavy-ion cancer therapy. Beam emittance and brightness values were calculated from data sets acquired for a variety of source parameters, in leaky as well as pulsed ion extraction mode. With box shaped pulses of C(4+) ions at an energy of 39 keV root mean square emittances of 1-4 mm mrad and a brightness of 10 nA mm(-2) mrad(-2) were achieved. The results meet the expectations for high quality ion beams generated by an electron beam ion source.
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